Preparation of superconducting-oxide films by CVD and their properties

The superconducting oxide films of Y-Ba-Cu-O(YBCO) and Bi-Sr-Ca-Cu-O (BSCCO) systems were prepared by CVD using β-diketone metal chelates and bismuth alkoxide as starting materials. Thermogravimetric analysis revealed that the chelates vaporized at a constant rate at a fixed evaporation temperature for several hours without decompositions. YBCO films grew epitaxially along the direction of the c-axis which was perpendicular to the single crystal SrTiO3(100) substrates at 800-9000C. Rectangular grains aligned two-dimensionally in the planes of these films. The films prepared at 8500C showed superconducting transition with zero resistivity at 93 K. The maximum current density was above 3x104A/cm2 at 77 K. NSCCO films were prepared on MgO(100) substrates at 7700C and were annealed at 8900C for 5 h under 1 atm of oxygen. The annealed films had a phase with c0=37 A as well as other phases in the BSCCO system. These films showed a mica-like grain structure. Superconducting transition began at 115 K and resistance started to drop at around 110 K attaining zero resistivity at 77 K